Desert Bighorn Sheep

Ovis canadensis nelsoni
Desert bighorn sheep ewe leaping / M. Weisenberger, USFWS

The desert bighorn has become well adapted to living in the desert heat and cold and, unlike most mammals, their body temperature can safely fluctuate several degrees. During the heat of the day, bighorn often rest in the shade of trees and caves. They are typically found in small scattered bands adapted to a desert mountain environment with little or no permanent water. Some of the bighorn may go without visiting a water source for weeks or months, sustaining their body moisture from food and from rainwater collected in temporary rock pools. They may have the ability to lose up to 30 percent of their body weight and still survive. After drinking water, they quickly recover from their dehydrated condition. Wildlife ecologists are just beginning to study the importance of this adaptive strategy, which has allowed these small bands to survive in areas too dry for many of their predators.

Desert bighorn are stocky, heavy-bodied sheep, similar in size to mule deer. Weights of mature rams range from 125 to 200 pounds, while ewes are somewhat smaller. Due to their unique padded hooves, bighorn are able to climb the steep, rocky terrain of the desert mountains with speed and agility. They rely on their keen eyesight to detect potential predators such as mountain lions, coyotes, and bobcats, and use their climbing ability to escape.  

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Both sexes develop horns soon after birth, with horn growth continuing more or less throughout life. Older rams have impressive sets of curling horns measuring over three feet long with more than one foot of circumference at the base. The ewes' horns are much smaller and lighter and do not tend to curl. The head and horns of an adult ram may weigh more than 30 pounds. Annual growth rings indicate the animal's age. Both rams and ewes use their horns as tools to break open cactus, which they consume, and for fighting. They feed on a wide variety of leaves, twigs, flowers, forbs, grasses, and cacti.

Rams battle to determine the dominant animal, which then gains possession of the ewes. Facing each other, rams charge head-on from distances of 20 feet or more, crashing their massive horns together with tremendous impact, until one or the other quits.

Bighorns live in separate ram and ewe bands most of the year. They gather during the breeding season (usually July-October), but breeding may occur anytime in the desert due to suitable climatic conditions. Gestation lasts about six months, and the lambs are usually born in late winter.

In the late 1800s and early 1900s bighorn sheep populations rapidly declined. Domestic cattle and sheep, along with wild horses and burros, competed with bighorns, especially at waterholes. Domestic stock also introduced diseases to bighorn populations. 

Facts About Desert Bighorn Sheep

Size: Males can reach up to 3 ½’ in height and up to 6’ long

Weight: Can weigh up to 200 pounds

Horns: Can weigh up to 30 pounds

Lifespan: As long as 12 years for males and 14 for females